Amy Malick

Experimental therapy of human glioma by means of a genetically engineered virus mutant

Malignant gliomas are the most common malignant brain tumors and are almost always fatal. A thymidine kinase-negative mutant of herpes simplex virus-1 (dlsptk) that is attenuated for neurovirulence was tested as a possible treatment for gliomas. In cell culture, dlsptk killed two long-term human glioma lines and three short-term human glioma cell populations. In nude mice with implanted subcutaneous and subrenal U87 human gliomas, intraneoplastic inoculation of dlsptk caused growth inhibition. In nude mice with intracranial U87 gliomas, intraneoplastic inoculation of dlsptk prolonged survival. Genetically engineered viruses such as dlsptk merit further evaluation as novel antineoplastic agents.

Reduction and elimination of encephalitis in an experimental glioma therapy model with attenuated herpes simplex mutants that retain susceptibility to acyclovir.

Malignant gliomas are the most common malignant brain tumors and are almost universally fatal. A genetically engineered herpes simplex virus-1 mutant with decreased neurovirulence, dlsptk, has been shown to kill human glioma cells in culture and in animal models. However, intracranial inoculation of dlsptk is limited by fatal encephalitis at higher doses. Therefore, additional engineered and recombinant herpes simplex mutants with demonstrated reduced neurovirulence (AraAr9, AraAr13, RE6, R3616) were examined as antiglioma agents. One long-term human glioma cell line and two early-passage human gliomas in culture were destroyed by all four viruses tested. In a subcutaneous glioma model, AraAr13, RE6, and R3616 retained substantial antineoplastic effects in nude mice when compared with controls (one-sided Wilcoxon rank test, P < 0.05 for one or more doses each). When tested in a nude mouse intracranial glioma model, both RE6 and R3616 significantly prolonged average survival without producing premature encephalitic deaths at two doses (log-rank statistic, P < 0.007). Histopathological studies of the brains of surviving animals revealed minimal focal encephalitis in two of three RE6-treated animals and no evidence of encephalitis in either one of three RE6-treated or in three of three R3616-treated animals. No evidence of residual tumor was seen in four of the six surviving animals. Additionally, both RE6 and R3616 were found to be susceptible to the common antiherpetic agent acyclovir, adding to their safety as potential antiglioma agents. Recombinant and engineered viruses that minimize host toxicity and maximize tumoricidal activity merit further study as antineoplastic agents.

A neurohistochemical blueprint for pain-induced loss of appetite

A common complaint among pain patients is that they lose their appetite. These accounts are anecdotal, however, and the neural mechanism underlying pain-induced loss of appetite remains unknown. In this study, we documented the occurrence of appetite loss in patients under migraine attack and investigated the neuronal substrate of pain-induced anorexia in our animal model of intracranial pain. We found that loss of appetite during the migraine attack in humans coincided strongly with the onset and duration of the head pain in 32/39 cases, and that brief noxious stimulation of the dura in conscious rats produced a transient suppression of food intake. Mapping of neuronal activation in the rat showed that noxious dural stimulation induced a 3- to 4-fold increase in the number of Fos-positive neurons in medullary dorsal horn areas that process nociceptive signals (laminae I, V) and in parabrachial and hypothalamic neurons positioned to suppress feeding behavior. In the parabrachial area, activated neurons were localized in the superior-lateral subnucleus, and 40% of them expressed the mRNA encoding the anorectic neuropeptide cholecystokinin. In the hypothalamus, activated Fos-positive neurons were found in the dorsomedial area of the ventromedial nucleus, and 76% of them expressed the mRNA for cholecystokinin type-B receptor. Based on these findings, we suggest that at least one of several groups of hypothalamic neurons that normally inhibit appetite in response to metabolic cues is positioned to mediate the suppression of food intake by pain signals.

Cells of origin of the trigeminohypothalamic tract in the rat

Recent studies have demonstrated that a large number of spinal cord neurons convey somatosensory and visceral nociceptive information directly from cervical, lumbar, and sacral spinal cord segments to the hypothalamus. Because sensory information from head and orofacial structures is processed by all subnuclei of the trigeminal brainstem nuclear complex (TBNC) we hypothesized that all of them contain neurons that project directly to the hypothalamus. In the present study, we used the retrograde tracer Fluoro‐Gold to examine this hypothesis. Fluoro‐Gold injections that filled most of the hypothalamus on one side labeled approximately 1,000 neurons (best case = 1,048, mean = 718 ± 240) bilaterally (70% contralateral) within all trigeminal subnuclei and C1–2. Of these neurons, 86% were distributed caudal to the obex (22% in C2, 22% in C1, 23% in subnucleus caudalis, and 18% in the transition zone between subnuclei caudalis and interpolaris), and 14% rostral to the obex (6% in subnucleus interpolaris, 4% in subnucleus oralis, and 4% in subnucleus principalis). Caudal to the obex, most labeled neurons were found in laminae I–II and V and the paratrigeminal nucleus, and fewer neurons in laminae III–IV and X. The distribution of retrogradely labeled neurons in TBNC gray matter areas that receive monosynaptic input from trigeminal primary afferent fibers innervating extracranial orofacial structures (such as the cornea, nose, tongue, teeth, lips, vibrissae, and skin) and intracranial structures (such as the meninges and cerebral blood vessels) suggests that sensory and nociceptive information originating in these tissues could be transferred to the hypothalamus directly by this pathway. J. Comp. Neurol. 400:125–144, 1998.